Heat sink

ABSTRACT

Provided herein is an example heat sink including a heat dissipation unit including a plurality of heat dissipation fin groups including a plurality of heat dissipation fins, the plurality of heat dissipation fin groups forming a laminated structure and a plurality of heat pipes, one end portions of which are thermally connected to a heating element and other end portions of which are inserted into a space provided between the plurality of heat dissipation fin groups forming the laminated structure and thermally connected to the heat dissipation unit.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalPatent Application No. PCT/JP2019/003084 filed on Jan. 30, 2019, whichclaims the benefit of Japanese Patent Application No. 2018-015334, filedon Jan. 31, 2018. The contents of these applications are incorporatedherein by reference in their entirety.

BACKGROUND Technical Field

The present disclosure relates to a heat sink that cools a heatingelement.

Background

As electronic apparatuses are provided with increasingly higherfunctions, heating elements such as electronic parts are mounted in ahigh density inside the electronic apparatuses. Heat sinks may be usedas units configured to cool heating elements such as electronic parts.As the above-described heat sink, for example, a fin integrated heatsink is available, which is provided with a base plate, a plurality ofheat dissipation fins positioned at a heat dissipation fin mounting unitformed on one side of the base plate and mechanically caulked and atleast one heat pipe positioned at a heat pipe mounting unit formed onanother side of the base plate, periphery of which is caulked (JapanesePatent Application Laid-Open No. 2004-96074).

When a heat sink is installed on a substrate inside a server or thelike, cooling is generally performed by forced air cooling using a fan.At this time, besides a heating element to be cooled by the heat sink(object to be cooled) on the substrate, other heating elements such asmany electronic parts may be present on the substrate upstream ofcooling air with respect to the object to be cooled. Since electronicparts or the like other than the heating element to be cooled by theheat sink are also mounted on the substrate like the heating element tobe cooled by the heat sink, a temperature of air around a place close tothe substrate rises by exchanging heat with other heating elementslocated upstream of the cooling air with respect to the object to becooled by the heat sink compared to air around a place far from thesubstrate.

Therefore, when a heating element is cooled by forced air cooling usinga fan, the temperature of the cooling air around an area far from thesubstrate is low, but high around an area close to the substrate, and sotemperature unevenness occurs in a height direction of the cooling air(direction substantially orthogonal to a flow direction of the coolingair). As described in Japanese Patent Application Laid-Open No.2004-96074, in the case of a heat sink in which a heat pipe extends inan extending direction of a base plate on which heat dissipation finsare disposed upright, if the above-described temperature unevennessoccurs in the height direction of the cooling air, heat dissipationdeteriorates in an area close to the base plate compared to an area farfrom the base plate, resulting in a situation in which heat dissipationcharacteristics of the heat sink deteriorate.

The present disclosure is related to providing a heat sink capable ofshowing excellent cooling performance on an object to be cooled evenwhen cooling air has a higher temperature in an area close to asubstrate than in an area far from the substrate.

SUMMARY

In accordance with one aspect of the present disclosure, a heat sinkincludes a heat dissipation unit provided with a heat dissipation fingroup including a plurality of heat dissipation fins and a heat pipe,one end portion of which is thermally connected to a heating element andanother end portion of which is thermally connected to the heatdissipation unit, in which the other end portion of the heat pipe isthermally connected to the heat dissipation unit at a position higherthan an installation surface of the heating element in a heightdirection of the heat dissipation fin group and the heat dissipation fingroup is provided at a position higher than the installation surface ofthe heating element in the height direction of the heat dissipation fingroup.

In the above-described aspect, the heat dissipation fin group ispositioned and the other end portion of the heat pipe is disposed at ahigh position in the height direction of the heat dissipation fin groupthat is supplied with cooling air, which is less affected by atemperature rise of the other heating element. Note that the “heightdirection of the heat dissipation fin group” in the presentspecification means a standing direction of a main surface of the heatdissipation fins.

In the heat sink according to the present disclosure, the plurality ofheat dissipation fin groups are provided at different positions in theheight direction of the heat dissipation fin group, the other endportion of at least one predetermined heat pipe among the plurality ofheat pipes is thermally connected to the heat dissipation fin groupformed at a highest position in the height direction of the heatdissipation fin group, the other end portions of the heat pipes otherthan the predetermined heat pipe among the plurality of heat pipes arethermally connected to the heat dissipation fin group formed at a lowposition in the height direction of the heat dissipation fin group thanthe heat dissipation fin group to which the other end portion of thepredetermined heat pipe is thermally connected.

In accordance with another aspect of the present disclosure, a heat sinkincludes a heat dissipation unit provided with a plurality of heatdissipation fin groups including a plurality of heat dissipation finswith the plurality of heat dissipation fin groups forming a laminatedstructure, a plurality of heat pipes, one end portions of which arethermally connected to a heating element and other end portions of whichare inserted into spaces provided among the plurality of heatdissipation fin groups that form the laminated structure and thermallyconnected to the heat dissipation unit, in which another end portion ofat least one predetermined heat pipe among the plurality of heat pipesis inserted into the space formed at a highest position in the heightdirection of the heat dissipation unit and other end portions of theheat pipes other than the predetermined heat pipe among the plurality ofheat pipes are inserted into the space formed at a lower position in theheight direction of the heat dissipation unit than the space into whichthe other end portion of the predetermined heat pipe is inserted.

In the above-described aspect, in the heat dissipation unit, other heatpipes are disposed at lower positions in the height direction of theheat dissipation unit supplied with cooling air heated by the otherheating elements other than the objects to be cooled by the heat sinkand the predetermined heat pipe is disposed at a higher position in theheight direction of the heat dissipation unit supplied with cooling air,which is less affected by the temperature rise by the other heatingelements. Note that the “height direction of the heat dissipation unit”in the present specification means a laminating direction of the heatdissipation fin groups, the “higher position in the height direction ofthe heat dissipation unit” means a position far from the heatingelement, which is an object to be cooled, and the “lower position in theheight direction of the heat dissipation unit” means a position close tothe heating element, which is an object to be cooled.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which one end portion of the predetermined heat pipeis thermally connected to a region where heat density of the heatingelement is higher than heat density of the one end portions of the otherheat pipes. Note that the “region of the heating element having higherheat density” in the present specification means a region on an outersurface of the heating element having a temperature higher than anaverage temperature of the entire outer surface of the heating element.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which the heat dissipation unit is provided with atleast a first heat dissipation fin group including a plurality of firstheat dissipation fins, a second heat dissipation fin group including aplurality of second heat dissipation fins and a third heat dissipationfin group including a plurality of third heat dissipation fins, thefirst heat dissipation fin group, the second heat dissipation fin groupand the third heat dissipation fin group form the laminated structure bythe second heat dissipation fin group facing the first heat dissipationfin group via the predetermined heat pipe, and the second heatdissipation fin group facing the third heat dissipation fin group viathe other heat pipes.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which the plurality of heat pipes are introducedfrom an opening side formed between the plurality of heat dissipationfins.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which the predetermined heat pipe is introduced froman opening side formed between the first heat dissipation fins.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which the other heat pipes are introduced from anopening side formed between the second heat dissipation fins.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which bent portions are formed in parts of theplurality of heat pipes thermally connected to the heat dissipationunit.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which the parts of the plurality of heat pipesthermally connected to the heat dissipation unit are processed into aflat shape.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which one end portion of the predetermined heat pipeand one end portions of the other heat pipes are disposed in parallel,thus the plurality of heat pipes forming heat pipe groups.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which one of the heat pipe groups is thermallyconnected to one of the heating element.

In accordance with a further aspect of the present disclosure, a heatsink is provided in which one or two of the heat pipe groups is/areprovided.

In the present disclosure, the other end portion of the heat pipe isthermally connected to the heat dissipation unit at a position higherthan an installation surface of the heating element in a heightdirection of the heat dissipation fin group and the heat dissipation fingroup is provided at a position higher than the installation surface ofthe heating element in the height direction of the heat dissipation fingroup, and so even when the cooling air supplied to the heat dissipationunit has a higher temperature at a lower position than at a higherposition in the height direction of the heat dissipation unit, the heatpipe is thermally connected to the region of the heat dissipation unitsupplied with cooling air having a low temperature. Therefore, since theheat pipe can show great heat transportation performance, it is possibleto show excellent cooling performance on an object to be cooled.

In the present disclosure, in the heat dissipation unit in which theplurality of heat dissipation fin groups are disposed at differentpositions in the height direction of the heat dissipation fin group, atleast one predetermined heat pipe is disposed at a high position and theother heat pipes are disposed at positions lower than the predeterminedheat pipe, and therefore even when the cooling air supplied to the heatdissipation unit has a higher temperature at a low position than at ahigh position in the height direction of the heat dissipation unit, thepredetermined heat pipe is thermally connected to the region of the heatdissipation unit supplied with cooling air having a low temperature.Therefore, since the predetermined heat pipe can show great heattransportation performance, it is possible to show excellent coolingperformance on an object to be cooled.

According to the aspect of the present disclosure, at least onepredetermined heat pipe among the plurality of heat pipes is disposed ata high position of the heat dissipation unit in which the heatdissipation fin group forms a laminated structure and the other heatpipes are disposed at positions lower than the predetermined heat pipe,and therefore even when the cooling air supplied to the heat dissipationunit has a higher temperature at a low position than at a high positionin the height direction of the heat dissipation unit, the predeterminedheat pipe is thermally connected to the region of the heat dissipationunit supplied with cooling air having a low temperature. Therefore,since the predetermined heat pipe can show great heat transportationperformance, it is possible to show excellent cooling performance on anobject to be cooled.

According to the aspect of the present disclosure, the one end portionof the predetermined heat pipe is thermally connected to a region of theheating element having higher heat density than the one end portions ofthe other heat pipes, and therefore since the predetermined heat pipecan reliably show great heat transportation performance, it is possibleto show more reliable cooling performance on an object to be cooled.

According to the aspect of the present disclosure, the second heatdissipation fin group faces the first heat dissipation fin group via thepredetermined heat pipe, the second heat dissipation fin group faces thethird heat dissipation fin group via the other heat pipes, and thereforeeven when a thermal load of the first heat dissipation fin group isdifferent from a thermal load of the third heat dissipation fin group,the second heat dissipation fin group can receive heat from a heat pipethermally connected to the heat dissipation fin group, which has beengiven a relatively large thermal load among the first heat dissipationfin group and the third heat dissipation fin group. Therefore, thethermal loads of the first heat dissipation fin group and the third heatdissipation fin group can be made uniform. Therefore, the second heatdissipation fin group can emit more heat from a heat pipe thermallyconnected to the heat dissipation fin group, which has been given arelatively large thermal load. According to the aspect of the presentdisclosure, the second heat dissipation fin group can emit more heatfrom the heat pipe thermally connected to the heat dissipation fingroup, which has been given a relatively large thermal load and canconsequently facilitate cooling of the heating element, and can therebyextend reliability of the heating element.

According to the aspect of the present disclosure, the heat pipes areintroduced from the opening sides formed between the plurality of heatdissipation fins, and it is thereby possible to cool not only the otherend portions of the heat pipes thermally connected to the heatdissipation unit and the heat dissipation unit but also the centralparts of the heat pipes with cooling air sent in a directionsubstantially parallel to the surface of the heat dissipation fins.Therefore, cooling performance of the heat sink further improves.

According to the aspect of the present disclosure, since the bentportions are formed at parts of the heat pipes thermally connected tothe heat dissipation unit, it is possible to reduce the size of the heatpipes in the longitudinal axis direction and thermally connect the heatpipes to the plurality of heat dissipation fins that form the heatdissipation fin group respectively.

According to the aspect of the present disclosure, since the parts ofthe heat pipes thermally connected to the heat dissipation unit areprocessed into a flat shape, the area of contact between the heatdissipation unit and the heat pipes increases, and cooling efficiencycan be thereby improved. The above-described flattening process canreduce pressure loss of the cooling air in the heat dissipation unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat sink according to a firstembodiment of the present disclosure;

FIG. 2 is an explanatory view of a front of the heat sink according tothe first embodiment of the present disclosure;

FIG. 3 is an explanatory view of an inside of a heat dissipation unit ofthe heat sink according to the first embodiment of the presentdisclosure; and

FIG. 4 is a perspective view of a heat sink according to a secondembodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, a heat sink according to a first embodiment of the presentdisclosure will be described with reference to the accompanyingdrawings. As shown in FIG. 1, a heat sink 1 according to the firstembodiment is provided with first heat pipes 11 thermally connected to afirst heating element (not shown) via a first heat receiving plate 31and second heat pipes 13 thermally connected to a second heating element(not shown) via a second heat receiving plate 32. Both of the first heatpipes 11 and the second heat pipes 13 are thermally connected to acommon heat dissipation unit 20 of the heat sink 1. The heat dissipationunit 20 is provided with a first heat dissipation fin group 22, a secondheat dissipation fin group 24 and a third heat dissipation fin group 26.

In FIG. 1, the first heat dissipation fin group 22, the second heatdissipation fin group 24 and the third heat dissipation fin group 26 arelaminated in a height direction of the heat dissipation unit 20. Thatis, the heat dissipation unit 20 has a laminated structure composed of aplurality of heat dissipation fin groups. Among the first heatdissipation fin group 22, the second heat dissipation fin group 24 andthe third heat dissipation fin group 26, the first heat dissipation fingroup 22 is located at an upwardly farthest position with respect to theinstallation surface of the heating element, that is, at a highestposition in the height direction of the heat dissipation unit 20. On theother hand, the third heat dissipation fin group 26 is located at aclosest position with respect to the installation surface of the heatingelement, that is, at a lowest position in the height direction of theheat dissipation unit 20.

A first space 61 is provided between the first heat dissipation fingroup 22 and the second heat dissipation fin group 24. A second space 62is provided between the second heat dissipation fin group 24 and thethird heat dissipation fin group 26. Therefore, the first space 61 isprovided at a position higher than the second space 62 in the heightdirection of the heat dissipation unit 20.

As shown in FIG. 1, a plurality of (five in FIG. 1) first heat pipes 11are disposed in parallel in a direction substantially orthogonal to alongitudinal axis direction, forming a first heat pipe group 12. All theplurality of neighboring first heat pipes 11 are disposed so as tolaterally face each other. One end portions of all the plurality offirst heat pipes 11 are thermally connected to the first heatingelement, and the one end portions of the first heat pipe group 12 arethereby thermally connected to the first heating element. In the heatsink 1, the one end portions of the first heat pipe group 12 areindirectly contacted with the surface of the first heating element viathe first heat receiving plate 31 to thereby thermally connect the oneend portions of the first heat pipe group 12 to the first heatingelement.

Among the plurality of first heat pipes 11, other end portions ofpredetermined first heat pipes 11-1 (two pipes in FIG. 1) are thermallyconnected to the first heat dissipation fin group 22 and the second heatdissipation fin group 24. In the heat sink 1, the other end portions ofthe predetermined first heat pipes 11-1 are inserted into the firstspace 61 provided between the first heat dissipation fin group 22 andthe second heat dissipation fin group 24, and the other end portions ofthe predetermined first heat pipes 11-1 are thereby thermally connectedto the first heat dissipation fin group 22 and the second heatdissipation fin group 24. Furthermore, among the plurality of first heatpipes 11, other end portions of other first heat pipes 11-2, which arenot the predetermined first heat pipes 11-1 (three heat pipes in FIG. 1)are thermally connected to the second heat dissipation fin group 24 andthe third heat dissipation fin group 26. In the heat sink 1, the otherend portions of the other first heat pipes 11-2 are inserted into thesecond space 62 provided between the second heat dissipation fin group24 and the third heat dissipation fin group 26, and the other endportions of the other first heat pipes 11-2 are thereby thermallyconnected to the second heat dissipation fin group 24 and the third heatdissipation fin group 26.

That is, as shown in FIGS. 1 and 2, among the plurality of first heatpipes 11, some of the first heat pipes (predetermined first heat pipes11-1) are thermally connected to the heat dissipation unit 20 at ahigher position in the height direction of the heat dissipation unit 20and the other first heat pipes (other first heat pipes 11-2) arethermally connected to the heat dissipation unit 20 at a lower positionin the height direction of the heat dissipation unit 20. In the heatsink 1, the predetermined first heat pipes 11-1 and the other first heatpipes 11-2 are alternately disposed.

As shown in FIG. 1, a plurality of (five in FIG. 1) second heat pipes 13are disposed in parallel in a direction substantially orthogonal to thelongitudinal axis direction, forming a second heat pipe group 14. Allthe plurality of second heat pipes 13 are disposed so as to laterallyface each other. One end portions of all the plurality of second heatpipes 13 are thermally connected to the second heating element, and theone end portions of the second heat pipe group 14 are thereby thermallyconnected to the second heating element. In the heat sink 1, the one endportions of the second heat pipe group 14 are indirectly contacted withthe surface of the second heating element via the second heat receivingplate 32 to thereby thermally connect the one end portions of the secondheat pipe group 14 to the second heating element.

Among the plurality of second heat pipes 13, other end portions ofpredetermined second heat pipes 13-1 (three heat pipes in FIG. 1) arethermally connected to the first heat dissipation fin group 22 and thesecond heat dissipation fin group 24. In the heat sink 1, the other endportions of the predetermined second heat pipes 13-1 are inserted intothe first space 61 provided between the first heat dissipation fin group22 and the second heat dissipation fin group 24, and the other endportions of the predetermined second heat pipes 13-1 are therebythermally connected to the first heat dissipation fin group 22 and thesecond heat dissipation fin group 24. Furthermore, among the pluralityof second heat pipes 13, other end portions of other second heat pipes13-2, which are not the predetermined second heat pipes 13-1 (two pipesin FIG. 1) are thermally connected to the second heat dissipation fingroup 24 and the third heat dissipation fin group 26. In the heat sink1, the other end portions of the other second heat pipes 13-2 areinserted into the second space 62 provided between the second heatdissipation fin group 24 and the third heat dissipation fin group 26,and the other end portions of the other second heat pipes 13-2 arethereby thermally connected to the second heat dissipation fin group 24and the third heat dissipation fin group 26.

That is, as shown in FIGS. 1 and 2, among the plurality of second heatpipes 13, some of the second heat pipes (predetermined second heat pipes13-1) are thermally connected to the heat dissipation unit 20 at ahigher position in the height direction of the heat dissipation unit 20and the other second heat pipes (other second heat pipes 13-2) arethermally connected to the heat dissipation unit 20 at a lower positionin the height direction of the heat dissipation unit 20. In the heatsink 1, the predetermined second heat pipes 13-1 and the other secondheat pipes 13-2 are alternately disposed.

Among the first heat pipes 11, the predetermined first heat pipes 11-1receive heat emitted from the first heating element via the first heatreceiving plate 31 at one end portions and transport the heat from theone end portions to the other end portions of the predetermined firstheat pipes 11-1. The heat transported to the other end portions of thepredetermined first heat pipes 11-1 is transmitted from the other endportions to the first heat dissipation fin group 22 and the second heatdissipation fin group 24 thermally connected to the other end portions.The other first heat pipes 11-2 receive the heat emitted from the firstheating element via the first heat receiving plate 31 at the one endportions and transport the heat from the one end portions to the otherend portions of the other first heat pipes 11-2. The heat transported tothe other end portions of the other first heat pipes 11-2 is transmittedfrom the other end portions to the second heat dissipation fin group 24and the third heat dissipation fin group 26 thermally connected to theother end portions. The heat transported from the first heating elementto the heat dissipation unit 20 via the first heat pipes 11 is emittedto the outside from the heat dissipation unit 20.

Among the second heat pipes 13, the predetermined second heat pipes 13-1receive heat emitted from the second heating element via the second heatreceiving plate 32 at one end portions and transport the heat from theone end portions to the other end portions of the predetermined secondheat pipes 13-1. The heat transported to the other end portions of thepredetermined second heat pipes 134 is transmitted from the other endportions to the first heat dissipation fin group 22 and the second heatdissipation fin group 24 thermally connected to the other end portions.The other second heat pipes 13-2 receive the heat emitted from thesecond heating element via the second heat receiving plate 32 at the oneend portions and transport the heat from the one end portions to theother end portions of the other second heat pipes 13-2. The heattransported to the other end portions of the other second heat pipes13-2 is transmitted from the other end portions to the second heatdissipation fin group 24 and the third heat dissipation fin group 26thermally connected to the other end portions. The heat transported fromthe second heating element to the heat dissipation unit 20 via thesecond heat pipes 13 is emitted to the outside from the heat dissipationunit 20.

As shown in FIG. 1, containers of the first heat pipes 11 and containersof the second heat pipes 13 in the heat sink 1 are tube members,cross-sections in a diameter direction of which are substantiallycircular. In order to improve thermal connectivity at the heat receivingportion of the first heat pipes 11, the first heat receiving plate 31 isprovided between the first heat pipe group 12 and the first heatingelement. In order to improve thermal connectivity at the heat receivingportion of the second heat pipes 13, the second heat receiving plate 32is provided between the second heat pipe group 14 and the second heatingelement.

In correspondence with the fact that the first heating element and thesecond heating element are disposed on substantially the same plane, theheat receiving portion of the first heat pipe group 12 and the heatreceiving portion of the second heat pipe group 14 in the heat sink 1are disposed on substantially the same plane.

As described above, the other end portion of each first heat pipe 11 isthermally connected to the heat dissipation unit 20, and the other endportion of the first heat pipe group 12 is thereby thermally connectedto the heat dissipation unit 20. The other end portion of each secondheat pipe 13 is thermally connected to the heat dissipation unit 20, andthe other end portion of the second heat pipe group 14 is therebythermally connected to the heat dissipation unit 20. All regions(central parts) between the one end portions and the other end portionsof the first heat pipe group 12 and the second heat pipe group 14 havelinear shapes in a plan view.

As shown in FIG. 1, the heat dissipation unit 20, an external shape ofwhich is a substantially rectangular parallelepiped, is provided withthe first heat dissipation fin group 22, an external shape of which is asubstantially rectangular parallelepiped, the second heat dissipationfin group 24 adjacent to the first heat dissipation fin group 22 and, anexternal shape of which is a substantially rectangular parallelepipedand the third heat dissipation fin group 26 adjacent to the second heatdissipation fin group 24 and, an external shape of which is asubstantially rectangular parallelepiped. Furthermore, the first heatdissipation fin group 22, the second heat dissipation fin group 24 andthe third heat dissipation fin group 26 are laminated one on another.That is, the heat dissipation unit 20 in the heat sink 1 has amultilayer structure including a plurality of heat dissipation fingroups laminated one on another, and since the heat dissipation unit 20in the heat sink 1 includes three heat dissipation fin groups, the heatdissipation unit 20 has a three-layer laminated structure.

The first heat dissipation fin group 22 is provided with a plurality offirst heat dissipation fins 21. The first heat dissipation fins 21 aredisposed in parallel in a direction substantially parallel to thelongitudinal direction of the heat dissipation unit 20. A main surfaceof each first heat dissipation fin 21 is disposed so as to besubstantially parallel to central parts of the first heat pipe group 12and the second heat pipe group 14, which have a linear shape in a planview. Therefore, the main surface of each first heat dissipation fin 21forms transverse directions of the heat dissipation unit 20 and thefirst heat dissipation fin group 22. The first heat dissipation fin 21is, for example, a member having a U-shaped cross section with anextending portion (not shown) extending from both upper and lower endsof the main surface and the first heat dissipation fin group 22 can beformed by connecting a locking piece of a distal end of the extendingportion to a receiving portion (not shown) of the other neighboringfirst heat dissipation fin 21 (connected by caulking or the like) orbonding the distal end of the extending portion to the other neighboringfirst heat dissipation fin 21 (bonding by soldering or the like).

The second heat dissipation fin group 24 is provided with a plurality ofsecond heat dissipation fins 23. The second heat dissipation fins 23 aredisposed in parallel in a direction substantially parallel to thelongitudinal direction of the heat dissipation unit 20. Furthermore, amain surface of each second heat dissipation fin 23 is disposed so as tobe substantially parallel to central parts of the first heat pipe group12 and the second heat pipe group 14, which have a linear shape in aplan view. Therefore, the main surface of each second heat dissipationfin 23 forms transverse directions of the heat dissipation unit 20 andthe second heat dissipation fin group 24. The second heat dissipationfin 23 is, for example, a member having a U-shaped cross section with anextending portion (not shown) extending from both upper and lower endsof the main surface and the second heat dissipation fin group 24 can beformed by connecting a locking piece of a distal end of the extendingportion to a receiving portion (not shown) of the other neighboringsecond heat dissipation fin 23 (connected by caulking or the like) orbonding the distal end of the extending portion to the other neighboringsecond heat dissipation fin 23 (bonding by soldering or the like).

In the first heat dissipation fin group 22, a first opening 51 is formedbetween one first heat dissipation fin 21 and another neighboring firstheat dissipation fin 21, and the predetermined first heat pipes 11-1 andthe predetermined second heat pipes 13-1 are introduced from the firstopening 51 side into the heat dissipation unit 20, that is, between thefirst heat dissipation fin group 22 and the second heat dissipation fingroup 24. In the second heat dissipation fin group 24, a second opening52 is formed between one second heat dissipation fin 23 and anotherneighboring second heat dissipation fin 23, and the predetermined firstheat pipes 11-1 and the predetermined second heat pipes 13-1 areintroduced from the second opening 52 side into the heat dissipationunit 20, that is, between the first heat dissipation fin group 22 andthe second heat dissipation fin group 24.

The main surface of each first heat dissipation fin 21 and the mainsurface of each second heat dissipation fin 23 are disposed in parallelwith central parts of the first heat pipe group 12 and the second heatpipe group 14, which have a linear shape in a plan view. Therefore, boththe first openings 51 and the second openings 52 are opened parallel tothe central parts of the first heat pipe group 12 and the second heatpipe group 14.

Therefore, in the heat sink 1, the predetermined first heat pipes 11-1and the predetermined second heat pipes 13-1 are introduced into theheat dissipation unit 20 from a direction parallel to the first openings51 and the second openings 52, that is, from a direction orthogonal tothe longitudinal direction of the heat dissipation unit 20.

The third heat dissipation fin group 26 is provided with a plurality ofthird heat dissipation fins 25. The third heat dissipation fins 25 aredisposed in parallel in a direction substantially parallel to thelongitudinal direction of the heat dissipation unit 20. A main surfaceof each third heat dissipation fin 25 is disposed in substantiallyparallel with central parts of the first heat pipe group 12 and thesecond heat pipe group 14, which have a linear shape in a plan view.Therefore, the main surface of each third heat dissipation fin 25 formstransverse directions of the heat dissipation unit 20 and the third heatdissipation fin group 26. The third heat dissipation fin 25 is, forexample, a member having a U-shaped cross section with an extendingportion (not shown) extending from both upper and lower ends of the mainsurface and the third heat dissipation fin group 26 can be formed byconnecting a locking piece of a distal end of the extending portion to areceiving portion (not shown) of the other neighboring third heatdissipation fin 25 (connected by caulking or the like) or bonding thedistal end of the extending portion to the other neighboring third heatdissipation fin 25 (bonding by soldering or the like).

In the third heat dissipation fin group 26, a third opening 53 is formedbetween one third heat dissipation fin 25 and another neighboring thirdheat dissipation fin 25, and the other first heat pipes 11-2 and theother second heat pipes 13-2 are introduced from the third opening 53side into the heat dissipation unit 20, that is, between the second heatdissipation fin group 24 and the third heat dissipation fin group 26.

The main surface of each third heat dissipation fin 25 is disposed inparallel with central parts of the first heat pipe group 12 and thesecond heat pipe group 14, which have a linear shape in a plan view.Therefore, the third opening 53 is also opened in parallel with thecentral portions of the first heat pipe group 12 and the second heatpipe group 14.

Therefore, in the heat sink 1, the other first heat pipes 11-2 and theother second heat pipes 13-2 are introduced into the heat dissipationunit 20 from a direction parallel to the second openings 52 and thethird openings 53, that is, from a direction orthogonal to thelongitudinal direction of the heat dissipation unit 20.

As shown in FIGS. 1 and 3, in the heat sink 1, bent portions 15 areformed in parts of the predetermined first heat pipes 11-1 and thepredetermined second heat pipes 13-1 thermally connected to the firstheat dissipation fin group 22 and the second heat dissipation fin group24. Therefore, both the predetermined first heat pipes 11-1 and thepredetermined second heat pipes 13-1 are substantially L-shaped in aplan view. The predetermined first heat pipes 11-1 are positioned at aleft side of the predetermined second heat pipes 13-1 and both bentportions 15 of the predetermined first heat pipes 11-1 are bentrightward. The two bent portions 15 at a left side of the predeterminedsecond heat pipes 13-1 are bent leftward and one bent portion 15 at aright side is bent rightward. Therefore, as shown in FIG. 3, with thebent portions 15, the other end portions of the predetermined first heatpipes 11-1 and the predetermined second heat pipes 13-1 are configuredto extend in substantially parallel with the longitudinal direction ofthe heat dissipation unit 20.

Though not illustrated, bent portions of the other first heat pipes 11-2and the other second heat pipes 13-2 are formed in parts thermallyconnected to the second heat dissipation fin group 24 and the third heatdissipation fin group 26. Therefore, both the other first heat pipes11-2 and the other second heat pipes 13-2 are substantially L-shaped ina plan view. The other first heat pipes 11-2 are positioned at a leftside of the other second heat pipes 13-2 and all the bent portions ofthe other first heat pipes 11-2 are bent rightward. The one bent portionon the left side of the other second heat pipes 13-2 is bent leftwardand the one bent portion on the right side is bent rightward. Thus, withthe bent portions, the other end portions of the other first heat pipes11-2 and the other second heat pipes 13-2 are configured to extend insubstantially parallel with the longitudinal direction of the heatdissipation unit 20. Therefore, it is possible to thermally connect thefirst heat pipes 11 and the second heat pipes 13 to the plurality ofheat dissipation fins of the heat dissipation unit 20 while reducing thesizes of the first heat pipes 11 and the second heat pipes 13 in thelongitudinal axis direction.

The other end portions of the first heat pipes 11 and the second heatpipes 13 thermally connected to the heat dissipation unit 20 areprocessed into a flat shape. The flattening process can increase theareas of contact between the heat dissipation unit 20 and the first heatpipes 11 and the second heat pipes 13, and improve cooling efficiency.The flattening process can reduce pressure loss of cooling air F in theheat dissipation unit 20.

Materials of the first heat dissipation fins 21, the second heatdissipation fins 23 and the third heat dissipation fins 25 are notparticularly limited, but metals such as copper, copper alloy, aluminum,or aluminum alloy can be taken as examples. Container materials of thefirst heat pipes 11 and the second heat pipes 13 are not particularlylimited, but metals such as copper, copper alloy, aluminum, aluminumalloy or stainless steel can be taken as examples. A method forthermally connecting the first heat dissipation fins 21, the second heatdissipation fins 23 and the third heat dissipation fins 25 to the firstheat pipes 11 and the second heat pipes 13 is not particularly limited,but the first heat dissipation fins 21, the second heat dissipation fins23 and the third heat dissipation fins 25 can be thermally connected tothe first heat pipes 11 and the second heat pipes 13 by bonding such assoldering. Examples of working fluid to be sealed in the first heatpipes 11 and the second heat pipes 13 include water, alternativechlorofluorocarbon, perfluorocarbon or cyclopentane.

As described above, in the heat sink 1, among the plurality of firstheat pipes 11 thermally connected to the first heating element, thepredetermined first heat pipes 11-1 are disposed at high positions ofthe heat dissipation unit 20 and the other first heat pipes 11-2 aredisposed at positions of the heat dissipation unit 20 lower than thepredetermined first heat pipes 11-1. Furthermore, among the plurality ofsecond heat pipes 13 thermally connected to the second heating element,the predetermined second heat pipes 13-1 are disposed at high positionsof the heat dissipation unit 20 and the other second heat pipes 13-2 aredisposed at positions of the heat dissipation unit 20 lower than thepredetermined second heat pipes 13-1. Therefore, even when the coolingair F has a higher temperature at a low position in the height directionof the heat dissipation unit 20 than at a high position, thepredetermined first heat pipes 11-1 and the predetermined second heatpipes 13-1 thermally connected to the region of the heat dissipationunit 20 supplied with the cooling air F having a low temperature canthereby show great heat transportation performance. In the heat sink 1,the predetermined first heat pipes 11-1 and the predetermined secondheat pipes 13-1 show great heat transportation performance, and canthereby show excellent cooling performance on the heating element.

Even when the cooling air F has a higher temperature at the low positionin the height direction of the heat dissipation unit 20 than at the highposition, the predetermined first heat pipes 11-1 and the predeterminedsecond heat pipes 13-1 show great heat transportation performance, andcan thereby uniformly cool each heating element even when a plurality ofheating elements are thermally connected to the heat sink 1.

In the heat sink 1, the predetermined first heat pipes 11-1 and theother first heat pipes 11-2 are alternately disposed, heat is therebyuniformly transmitted from the entire first heat receiving plate 31thermally connected to the first heating element to the first heat pipegroup 12. Thus, cooling efficiency with respect to the first heatingelement improves more in the heat sink 1. Furthermore, since thepredetermined second heat pipes 13-1 and the other second heat pipes13-2 are alternately disposed, heat is thereby uniformly transmittedfrom the entire second heat receiving plate 32 thermally connected tothe second heating element to the second heat pipe group 14. Thus,cooling efficiency with respect to the second heating element improvesmore in the heat sink 1.

In the heat sink 1, among the plurality of first heat pipes 11, thepredetermined first heat pipes 11-1 and the other first heat pipes 11-2are thermally connected to the heat dissipation unit 20 at differentheights, and therefore, compared to a case where all the plurality offirst heat pipes 11 are thermally connected to the heat dissipation unit20 at the same height, the bent portions of the first heat pipes 11 canbe accommodated compactly. Similarly, in the heat sink 1, compared to acase where all the plurality of second heat pipes 13 are thermallyconnected to the heat dissipation unit 20 at the same height, the bentportions of the second heat pipes 13 can be accommodated compactly.Therefore, in the heat sink 1, since space can be saved in the bentportions of the first heat pipes 11 and the second heat pipes 13, theheat sink 1 can be mounted in a housing even when electronic parts orthe like are mounted in the housing at high density.

In the heat sink 1, the second heat dissipation fin group 24 faces thefirst heat dissipation fin group 22 via the predetermined heat pipes andthe second heat dissipation fin group 24 faces the third heatdissipation fin group 26 via the other heat pipes, and even when athermal load of the first heat dissipation fin group 22 differs from athermal load of the third heat dissipation fin group 26, the second heatdissipation fin group 24 can receive heat from heat pipes thermallyconnected to the heat dissipation fin group given a relatively largethermal load of the first heat dissipation fin group 22 and the thirdheat dissipation fin group 26. Therefore, in the heat sink 1, it ispossible to uniformize thermal loads of the first heat dissipation fingroup 22 and the third heat dissipation fin group 26. As describedabove, the second heat dissipation fin group 24 can emit more heat fromthe heat pipes thermally connected to the heat dissipation fin groupgiven a relatively large thermal load. In the heat sink 1, the secondheat dissipation fin group can emit more heat from the heat pipesthermally connected to the heat dissipation fin group given a relativelylarge thermal load, consequently facilitate cooling of the heatingelement, and thereby extend reliability of the heating element.

In the heat sink 1, since the first heat pipes 11 and the second heatpipes 13 are introduced from the opening side formed between theplurality of heat dissipation fins, is possible to cool not only theother end portions of the first heat pipes 11 and the second heat pipes13 thermally connected to the heat dissipation unit 20 and the heatdissipation unit 20 but also the central parts of the first heat pipes11 and the second heat pipes 13 with the cooling air F sent insubstantially parallel with the main surfaces of the heat dissipationfins. Therefore, cooling performance of the heat sink 1 furtherimproves.

Next, a heat sink according to a second embodiment of the presentdisclosure will be described with reference to the accompanyingdrawings. Note that the same components as the components of the heatsink 1 according to the first embodiment will be described using thesame reference numerals.

In the heat sink 1 according to the first embodiment, the predeterminedfirst heat pipes 11-1 and the other first heat pipes 11-2 are disposedalternately. Instead of this, as shown in FIG. 4, in a heat sink 2according to the second embodiment, predetermined first heat pipes 11-1are disposed in parallel in the central part and other first heat pipes11-2 are disposed on both sides of the predetermined first heat pipes11-1. In the heat sink 2, predetermined second heat pipes 13-1 aredisposed in parallel in the central part and other second heat pipes13-2 are disposed on both sides of the predetermined second heat pipes13-1.

The heat sink 2 can show cooling performance on the heating element morereliably when a region of high heat density (e.g., hot spot) is formednear the central part of the surface of the first heat receiving plate31 and the surface of the second heat receiving plate 32. That is, theheat sink 2 can show cooling performance on the heating element morereliably in that the one end portions of the predetermined heat pipesshowing great heat transportation performance are thermally connected tothe region of the heat receiving plate of high heat density than the oneend portions of the other heat pipes. Note that the “region of the heatreceiving plate of high heat density” means a region at a temperaturehigher than an average temperature of the entire surface of the surfaceof the heat receiving plate.

Next, other embodiments of the heat sink of the present disclosure willbe described. Although the number of heat pipes forming the first heatpipe group and the second heat pipe group is 5 in the above-describedembodiments, the number of heat pipes in each heat pipe group can beselected as appropriate in accordance with a heating value or the likeof the heating element as long as the number of heat pipes is plural,such as 2 to 4 or 6 or more. The number of first heat pipes forming thefirst heat pipe group and the number of second heat pipes forming thesecond heat pipe group may be the same or different.

Although two heat pipe groups are provided in the above-describedembodiments in correspondence with the fact that the number of heatingelements is 2, the number of heat pipe groups and the number of heatingelements are not particularly limited, and for example, the number maybe 1 or 3 or more.

Although the heat dissipation fin groups of the heat dissipation unit inthe above-described embodiments have a three-layer structure includingthree heat dissipation fin groups, the heat dissipation fin groups mayhave a four-layer structure including four heat dissipation fin groupsor a structure having 5 or more layers including 5 or more heatdissipation fin groups. A heat dissipation unit having a 4-layerstructure includes 3 spaces provided between neighboring heatdissipation fin groups and a heat dissipation unit having a structure of5 or more layers includes 4 or more spaces provided between neighboringheat dissipation fin groups. At least one heat pipe out of one heat pipegroup may be inserted in the above-described space formed at a highestposition in the height direction of the heat dissipation unit. In otherwords, the number of predetermined heat pipes per heat pipe group may beat least one and at least one heat pipe of at least one of the firstheat pipes and the second heat pipes may be inserted in theabove-described space at a position other than the highest position.

Although the heat dissipation unit in the above-described embodiments isprovided with a plurality of heat dissipation fin groups and a pluralityof heat pipes, the number of heat dissipation fin groups may be one orwhen the number of heat dissipation fin groups is one, the number ofheat pipes may be one or plural. In this case, the other end portions ofthe heat pipes are thermally connected to the heat dissipation unit(heat dissipation fin group) at positions higher than the installationsurface of the heating element in the height direction of the heatdissipation fin group and the heat dissipation unit (heat dissipationfin group) is provided at a position higher than the installationsurface of the heating element in the height direction of the heatdissipation fin group. That is, the heat dissipation unit (heatdissipation fin group) is provided only at a position higher than theinstallation surface of the heating element in the height direction ofthe heat dissipation fin group.

In the above-described aspect, even when the cooling air supplied to theheat dissipation unit has a higher temperature at a low position than ata high position in the height direction of the heat dissipation unit,the heat pipes are thermally connected to the region of the heatdissipation unit supplied with cooling air having a low temperature.Therefore, the heat pipes can show great heat transportationperformance, and can thereby show excellent cooling performance on theobject to be cooled.

In the above-described embodiments, the heat dissipation unit has alaminated structure including a plurality of heat dissipation fingroups, but the plurality of heat dissipation fin groups are not limitedto the formation of the laminated structure, and the plurality of heatdissipation fin groups need only to be provided at different positions,that is, at different heights in the height direction of the heatdissipation fin group. As an aspect in which the plurality of heatdissipation fin groups are provided at different heights without formingthe laminated structure, an aspect in which the plurality of heatdissipation fin groups are disposed in a stepwise shape can be taken asan example.

In this case, the other end portion of at least one predetermined heatpipe among the plurality of heat pipes is thermally connected to theheat dissipation fin group formed at a highest position in the heightdirection of the heat dissipation fin group and the other end portionsof the heat pipes other than the predetermined heat pipe among theplurality of heat pipes are thermally connected to the heat dissipationfin group formed at a position in the height direction of the heatdissipation fin group lower than the heat dissipation fin group to whichthe other end portion of the predetermined heat pipe is thermallyconnected.

In the above-described aspect, as in the cases of the above-describedembodiments, even when the cooling air supplied to the heat dissipationunit has a higher temperature at a low position than at a high positionin the height direction of the heat dissipation unit, the predeterminedheat pipe is thermally connected to the region of the heat dissipationunit supplied with cooling air having a low temperature. Therefore, thepredetermined heat pipe can show great heat transportation performance,and can thereby show excellent cooling performance on the object to becooled.

While the heat sink of the present disclosure can be used in a widerange of fields, even when unevenness occurs in the temperature ofcooling air in the height direction of the heat dissipation unit, thepredetermined heat pipe shows great heat transportation performance, andcan thereby show excellent cooling performance on the object to becooled. Therefore, the heat sink of the present disclosure has a highutility value in the field of cooling electronic parts such asarithmetic elements mounted on a server.

What is claimed is:
 1. A heat sink comprising: a heat dissipation unitcomprising a plurality of heat dissipation fin groups including aplurality of heat dissipation fins, the plurality of heat dissipationfin groups forming a laminated structure; and a plurality of heat pipes,one end portions of which are thermally connected to a heating elementand other end portions of which are inserted into a space providedbetween the plurality of heat dissipation fin groups forming thelaminated structure and thermally connected to the heat dissipationunit, wherein another end portion of at least one predetermined heatpipe among the plurality of heat pipes is inserted into a space formedat a highest position in a height direction of the heat dissipationunit, and other end portions of heat pipes other than the at least onepredetermined heat pipe among the plurality of heat pipes are insertedinto a space formed at a position in the height direction of the heatdissipation unit lower than the space into which the another end portionof the at least one predetermined heat pipe is inserted.
 2. The heatsink according to claim 1, wherein one end portion of the at least onepredetermined heat pipe is thermally connected to a region where heatdensity of the heating element is higher than heat density of one endportions of the heat pipes other than the at least one predeterminedheat pipe.
 3. The heat sink according to claim 1, wherein the heatdissipation unit comprises at least a first heat dissipation fin groupincluding a plurality of first heat dissipation fins, a second heatdissipation fin group including a plurality of second heat dissipationfins, and a third heat dissipation fin group including a plurality ofthird heat dissipation fins, and the first heat dissipation fin group,the second heat dissipation fin group and the third heat dissipation fingroup form the laminated structure by the second heat dissipation fingroup facing the first heat dissipation fin group via the at least onepredetermined heat pipe, and the second heat dissipation fin groupfacing the third heat dissipation fin group via the heat pipes otherthan the at least one predetermined heat pipe.
 4. The heat sinkaccording to claim 1, wherein the plurality of heat pipes are introducedfrom an opening side formed between the plurality of heat dissipationfins.
 5. The heat sink according to claim 3, wherein the at least onepredetermined heat pipe is introduced from an opening side formedbetween the first heat dissipation fins.
 6. The heat sink according toclaim 3, wherein the heat pipes other than the at least onepredetermined heat pipe are introduced from an opening side formedbetween the second heat dissipation fins.
 7. The heat sink according toclaim 1, wherein bent portions are formed in parts of the plurality ofheat pipes thermally connected to the heat dissipation unit.
 8. The heatsink according to claim 1, wherein parts of the plurality of heat pipesthermally connected to the heat dissipation unit are processed into aflat shape.
 9. The heat sink according to claim 1, wherein the pluralityof heat pipes form heat pipe groups by one end portion of the at leastone predetermined heat pipe and one end portions of the heat pipes otherthan the at least one predetermined heat pipe being disposed inparallel.
 10. The heat sink according to claim 9, wherein one of theheat pipe groups is thermally connected to one of the heating element.11. The heat sink according to claim 10, wherein one or two of the heatpipe groups is/are provided.